1. Field of the Invention
The present invention relates to fluid pressure actuated draw pad pressure control in drawing presses.
2. Prior Art
U.S. Pat. No. 3,908,429 illustrates a type of servovalve controlled hydraulic cupping press which includes hydraulically operated rams, hold down and blanking cylinders, and which provides precise feedback of the draw punch position for controlling of the various pressures.
In converting existing mechanical type presses, as well as existing hydraulic presses to have hydraulically actuating blanking and draw pad cylinders, it has been found the assemblies can be simplified by utilization of a unique swivel in the draw pad which is made of a confined elastomeric material.
Various types of elastomeric pads have been investigated. For example U.S. Pat. No. 2,108,746 shows a safety device for machine parts which utilizes an elastomeric material that is capable of flowing when a predetermined pressure limit is reached.
U.S. Pat. No. 216,551 illustrates a fifth wheel for a vehicle which has a ring of elastomeric material in it to prevent rattling and noise.
Other devices which use elastomeric material which is partially constrained to form a combined spring and damper to reduce noise and vibration include U.S. Pat. Nos. 1,660,676; 2,256,984; 2,547,725; and 2,697,578.